In certain sports, the transfer of body weight is considered the core of training. For example, in baseball the swing movement, the weight is first transferred to the back leg and then moved forward to generate energy. At the same time the back ankle starts rotation along with the back knee and the hip, which in turn bring the upper body, shoulder and arm to also rotate around the center of the body. In this process, the upward strength generated from the back leg (vertical) and the rotational strength of the hip (horizontal) are considered the key to a powerful swing.
The same is true for tennis and golf, where strength of the lower body generates the power for the swing action. U.S. Pat. No. 8,210,963 provides a device for improving golf swing by measuring the shift of golfer's body weight during a golf swing and comparing that to a technically sound swing. However, such device does not train or improve the user's lower body strength or rotational strength.
U.S. Pat. No. 8,187,153 provides an exercising machine for exercising a user's torso, arm, leg with computer-controlled resistance actuator. However, such device is complicated in structure, thus costly, and not easy to setup and use in a field training, such as a batting cage practice.
U.S. Pat. No. 8,162,807 describes a typical training device where weight is added to different part of the training device so as to work a particular part of the body. However, such device trainings the body only along one axis, and it is of no practical use in a field training.
U.S. Pat. No. 7,887,463 describes another typical leg training device that includes ski trainers, striders, steppers, elliptical trainers and exercise bikes. In this type of device the user steps on a carrier for each foot and exercises the leg by striding against resistance. However, this type of device does not work on the torso strength, especially on the rotation strength.
U.S. Pat. No. 7,775,914 only addresses the positioning of a baseball player's feet when swinging the bat. U.S. Pat. No. 6,773,366 only addresses the upper body training, especially the relative position of both arms during a swing.
U.S. Pat. No. 7,758,436 describes a swinging and hitting training aid for batters and golfers. It is a resistance-type indicator intended for a coach to determine whether the batter or golfer performs a proper swing. Little, if any, muscle strength is improved using this device.
U.S. Pat. No. 7,632,192 provides a multi-sport training device for improving hitting skills. However, insufficient resistance could be provided by the device, and a customized bat/club/racket must be provided in order to work with such device, making it impractical.
U.S. Pat. No. 7,625,320 provides a resistance swing training device that targets the hip rotation. However, that device has a large footprint and complicated structure, which is not easy to set up for field practice. Additionally, that device only provides resistance on the horizontal plane for rotation, without simultaneously addressing the issue of improving the vertical strength from the leg.
U.S. Pat. No. 7,438,653 describes another swing training device where a flexible rope is connected to a belt worn by a user. However, the position where the rope connects the belt is not fixed but instead a sliding connection, which effectively defeats the purpose of it because the sliding connection will significantly reduce the resistance from the rope. In addition, the fact that it does not provide a base is a disadvantage because fixing the rope on any object means the length of the rope needs to be constantly adjusted, and finding a fixture around a training site to tie the rope to is not always easy.
Therefore, there remains the need for a device and method for training an athlete in a sport that requires the hip rotation and lower body strength. There is also the need for the device being easy to set up in field practice and not hindering the normal swinging pattern.